The alliance was formed in 2004 to propel Zinifex to owner operatorship at the northwest Queensland mine.

Management from both companies have agreed to dissolve the alliance, which has developed the Century mine into a 1 million tonne per annum zinc and lead metal producer.

According to Zinifex, the mine generated $1.4 billion in revenue for the 2007 financial year.

As part of the mutual alliance dissolution, Zinifex will absorb Downer employees.

"Zinifex Century Mine values the contribution made by Downer EDI employees to the success of the mine - for that reason Zinifex intends to offer jobs to all current Downer EDI Mining employees," Zinifex Century Mine managing director John Lamb said.

"They will be transferred across to Zinifex over this 12-month period and will become Zinifex employees," he added.

Zinifex is currently in merger proceedings worth $6.2 billion with global mining house Oxiana, forming a major diversified base and precious metals mining entity.

Zinifex shares slipped 19c to $9.91 in early afternoon trade.